Open Day '08: the view from the pit

14 April 2008

A tour group prepares to visit the ATLAS Detector

A total of 5,700 people took the lift down heading 75 meters underground last weekend, as ATLAS opened its doors for CERN  Open Days.  Despite the queues, inevitable given the sheer number of visitors, the public was given a rare opportunity to see the biggest machine in the world and to witness the inner workings of the international collaboration.

“I think the event was a huge success. The teams of volunteers worked together really well and there was a great atmosphere,” said Sue Cheatham volunteer and ATLAS physicist. “There was not much elbow room in the ATLAS lift, but it was much better than telecabines out in the Alps!”

A very efficient team of volunteers stood in front of the lift access area to hand out helmets. Each group went down with a different color such that each group was easily identified. No time was wasted there and each set of helmets were counted, making sure nobody got lost.

At any one time, two groups of about 25 people each were admiring the detector, as the lift ferried people up and down almost non stop. And the guides down there had precious few minutes to answer questions about the experiment. One guide explained that ATLAS had many layers, just like Shrek!

“One of the most difficult things is trying to answer the visitor’s questions in a short and concise yet understandable way,” said ATLAS physicist and underground volunteer Tom Barber. These volunteers were bombarded with a whole host of questions - from whether we were going to blow up the world to whether we are going to discover antimatter. When it was explained to one group how the trigger system in ATLAS rejects a large proportion of events so that only the few interesting ones would be recorded for analysis, one visitor asked concernedly if all these millions events would pile up and so contaminate the environment.  Another group asked, since the calorimeter absorbs so many particles, when would we have to empty it out and where?

SLIMOS, the ATLAS safety team worked furiously to make sure the services ran smoothly and nothing went wrong. Their attention was needed just once on Sunday morning, when an alarm concerning the lift showed up on the control monitoring console, saying “Alarm Ascenseur CRAS-xxx PX15”. Although this was almost certainly due to someone accidentally pressing the alarm button the safety team had to stop people from going underground for just a minute whilst they made sure. “I found that the ‘CRAS part of the alarm message was a bit too close to ‘CRASH’!” said Giuseppe Mornacchi. After a brief check of all systems, everything was on the move again within minutes.

“I thoroughly enjoyed the day,” said Helfried Burckhart, organiser of the ATLAS open days. When I asked whether he had recovered from it all he replied that there was still much work to be done. “A lot of people worked very hard and now they all must be thanked. I can’t forget anyone!”

Colin Barras


Kate Shaw

University of Sheffield